Gypsy Moth
Gypsy moths were introduced into the United States in 1869 and were first detected in Wisconsin in the mid-1970s. Each year the caterpillars defoliate thousands of acres of trees in both urban and rural settings throughout the northeast United States. The eastern half of Wisconsin is recognized as infested and quarantines have been placed on wood product exports from those counties.
Gypsy moth caterpillars in your trees can be a real nuisance. When populations are high the caterpillars seem to be everywhere. Their feeding stresses and may kill valuable trees. You cannot eliminate every gypsy moth in your yard, but you can take some simple steps to cut their numbers.
For more information, or if you think you have found a gypsy moth, call your local forester, county agent, agricultural agent, or check the following web sites. 
Wisconsin Gypsy Moth
Wisconsin Department of Natural Resources
UW Extension
Wisconsin Department of Agriculture, Trade and Consumer Protection